In tank and apparatus construction, various vessel heads are known. Vessel heads tend to be vaulted sheet metal elements which serve to close the ends of usually cylindrical vessels or to subdivide the same into a number of compartments.
The actual vessels are usually cylindrical in shape, showing different cross-sections (e.g. circular, elliptical, dual-shell, quadruple-shell, box-shaped). The outer vessel wall is formed of one or more curved sheet metal element(s) (manufactured by rolling), showing a tubular shape and the pertaining cross-sectional geometry. The ends of such a shell ring are closed with suitable vessel heads. To this end the vessel heads are usually welded to the shell ring. To this end the vessel head comprises a connecting contour corresponding to the shell ring so that the shell and the head abut one another at their respective connecting contours and they can be connected with one another by way of a butt seam that is advantageous in terms of manufacturing and strength. There are connecting configurations where the vessel head is pushed into or onto the shell ring and the two components are connected by way of a so-called fillet weld. Other than cylindrically formed vessel rings there are also truncated-cone configurations.
The vessel heads show as a rule a cylindrical respectively conical rim or straight flange which makes a transition via a comparatively narrowly curved (torically vaulted) knuckle area to a flatter—often spherical—vaulted dish area forming the majority of the surface of the actual head.
In the case of vessels showing circular cross-sections, so-called torispherical dished heads are usually used which show a dished head shape according to DIN 28011, a torispherically dished head shape according to DIN 28013 (type: Korbbogen), or which are configured as an elliptical head respectively a normal/slightly vaulted head.
These heads tend to be manufactured in a two-stage process where—starting out from a flat sheet metal disk (circular or sheet blank)—first the spherical vault is formed in a pressing process (dishing) and thereafter the knuckle area and the so-called straight flange are integrally formed in a pressing process (flanging). Thin-walled heads may also be manufactured completely in one pressing process (usually deep drawing).
Manufacturing these vaulted heads is particularly challenging for non-circular tank cross-sections. These heads are known e.g. from DE 200 05 521 U. For one, the largely mechanised dishing and flanging processes for circular cylindrical heads cannot be employed. What is particularly difficult is integrally flanging, integrally forming the knuckle area and the straight flange. For another, the usual head shapes where a uniform vault radius makes a transition to a uniform knuckle radius in the dish area are suitable only to a limited extent for pressing and in particular deep-drawing processes since the shapes of non-circular vessel cross-sections show different and asymmetrical curve shapes which, together with the productional, asymmetrical strengths of rolled metal sheets may result in deformation anomalies. These may include creases, dents, and unintentional thinning or thickening in the starting material generated in the deformation process. Therefore these heads are manufactured in complex, manual shaping processes or joined together from prefabricated component parts. An end head area assembled from component parts for a transport vessel is e.g. known from EP 0 399 099 A.
For reasons of quality and efficiency it is therefore desirable to manufacture these kinds of heads—for example for elliptical, box-shaped or other, asymmetrical cross-sections—having differently contour curves in a defined tool with reproducible geometry to ensure the precisely fitting connection with shell rings likewise produced, without complicated refinishing work. There is a particular need in particular for deep-drawn vessel heads showing a wall thickness of more than 2 mm and suitable for vessel cross-sections having diameters in the magnitude of more than 500 mm in one axial direction and more than 1000 mm in another axial direction and which, given a narrow knuckle radius of about 50 to 75 mm, show a vault depth of more than 250 mm.
These vessel heads cannot be manufactured with simple deep-drawing processes (one-stage) at all or at best showing the quality defects indicated above. Although multi-stage deep-drawing processes where the desired geometry is configured in steps in multiple different tools and in multiple method steps may be suitable, they are economically feasible only in an industrial scale (in thousands).
Therefore there is the object to provide a non-round vessel head which can be manufactured in a one-stage deep-drawing process even given a relatively high wall thickness and comparatively large dimensions, and the final geometry of which can be manufactured with high repeating accuracy and narrow tolerances with a suitable method and using a suitable tool.